Re-potting your bonsai is an important part of bonsai care. After a certain amount of time, the roots of your bonsai will begin to fill the pot and your tree will be in need of your assistance. Re-potting is generally carried out every year or two during spring, but this could be different depending on the type and age of the tree. Re-potting with fresh soil will give your bonsai the nutrients it needs to thrive. Re-potting also allows you to trim the roots before the bonsai goes back into its container. Trimming roots creates space so your tree can go back into the pot. Another reason why we root prune is to encourage new feeder roots to grow throughout the coming year. Below you see how straight forward the process can be!
The tree below is due for a re-pot. The first step in re-potting is to get yourself prepared (never re-pot on the fly).
Below are some common bonsai tools that are used when re-potting. I have included some basic tools that you're more likely to have at home.
Once you have your tools handy, its time to prepare the pot. I have chosen a simple yet suitable pot for this maple bonsai. I am also preparing the mesh which will prevent soil from falling out of the pot.
Wire is used to secure the bonsai and to hold the mesh in place. Some bonsai pots will only have the one drainage hole, so I will only use one drainage hole to show you how it can be done!
The wire is fashioned into a butterfly shape
Insert the wire piece you have made through the main drainage hole. You can see here that I have already placed down my mesh pieces.
Once the pointed ends of the wire have been pushed through the drainage hole, bend the ends of wire flat against the bottom of the pot.
Flatten the loops at the top to secure the mesh.
Now we have to prepare the wire that will secure the bonsai to its pot. Below you can see a length of wire that will be used. The length of wire you will need and how thick the piece of wire will be depends on how large the bonsai is. Here I have used 1.5 mm wire.
The wire is inserted through the main drainage hole from the bottom of the pot. Normally, we would use wire holes which are on most bonsai pots, but not every pot has these.
The pot can now be partially filled with bonsai soil. There are many recipes for bonsai soil, and most are acceptable as long as the soil encourages excellent drainage. Here, I have used outdoor potting mix with coarse pumice. Most fine particles have been removed with a 2 mm sieve. It is important to remove fine particles as they can impair drainage and this will ultimately cause a decline in the health of the tree.
The pot has been partially filled with soil and is ready for the bonsai.
Back to our maple. Bonsai are often tied to a pot with wire. If that is the case, cut the wire at the base of the pot so the tree can be removed. This pot doesn't have wire that needs to be cut, instead it is being secured using a butterfly wire piece. We need to lift up this wire that is flat against the pot so we can remove the tree.
You may come across a pot which has wide edges and so it is difficult, if not impossible to pull the tree out of the pot in one piece (this pot is a perfect example). One solution to this issue is to use a long flat tool such as an old knife. Slide the knife down the edge of the pot and continue to cut around the edges so you can safely lift the bonsai out.
Wiggle the tree out of its pot. You should feel the whole root ball moving. If it feels like you're not going to get the whole root ball out, or if you feel that you're tearing the root ball in half trying to get the tree out, then continue to scrape the side of the pot with your flat tool.
The tree is starting to come loose now.
Great! The tree is out of its pot. Now we can go to work on the roots.
Using a weed hook, this is a great time to remove any weeds that are well rooted in amongst the bonsai soil.
Old soil is then removed from the roots of the tree with the help of a root rake, or this weeding tool. Once you have removed a decent amount of soil, you can now remove up to a third of the roots with some scissors. If you're re-potting a conifer such as a Pine or Juniper, try to only remove about a third of the soil and roots.
Now we can finally place our bonsai into its new pot. Because we prepared our pot and soil earlier, it can go in straight away. Be cautious of re-potting when temperatures a high, as the roots may dry out while the tree is out of its pot. Keep your bonsai in the shade and sprinkle the roots with some water if you have forgotten to prepare the pot in advance.
The bonsai is placed on top of the soil mound, and with some light downward pressure, I swivel the tree left and right into the soil.
Our wire that we prepared earlier is ready to secure our tree. Before we secure our tree though, we need to consider bonsai placement. I had decided to place the bonsai slightly off centre to the left. This creates a more natural appearance as opposed to placing the tree dead centre. Placing the tree to the left also counter balances the lowest branch which extends quite far to the right.
Now that we've decided on the trees position, we can secure the bonsai to its pot. Take your wire and begin to cross it over.
Try not to tie the wire over any root that you plan on showing above soil level. If I tighten the wire over these large roots, it may tear the bark off them. Instead, I have gone under them.
Pull in opposing directions and then twist the wire a few times to secure. Make sure to get a good firm hold. Until the roots secure themselves, the wire will be the first defence against wind and accidental knocks which would otherwise fling your bonsai from its pot.
Cut the wire
Top up with additional bonsai soil
After the bonsai soil has been added, we use a chopstick to fill in any air spaces, and to ensure good soil to root contact. This step is very important.
In small, quick movements, move your hand left and right with the chop stick. You will see the soil fill the air spaces. You may need to top up your soil as the soil lightly compresses.
Once we have spent some time filling in air spaces. We can now apply a top dressing to our bonsai. Top dressing is finer than bonsai soil, and is used to create an aesthetically pleasing appearance. Be sure to avoid adding any dust particles.
A touch of decorative moss and we're done! (almost)
Give the bonsai a good water and place it in a mostly shaded spot for a week or so. After a week, gradually introduce your bonsai back into the sunlight.
- Re-pot your tree from late winter to mid-spring depending on the tree species. Re-potting your bonsai out of season will lower your chances of a successful re-potting.
- As a general rule. Don’t prune more than one-third of the root ball.
- Wire your tree's roots to the pot as this will stop the wind from blowing it out of the pot.
- Make sure to ‘work in’ the new soil around the roots after the re-pot. The roots should have good contact with the soil and there shouldn't be any large air pockets.
- Water the bonsai thoroughly after re-potting.
- Keep the bonsai in a shaded spot for a week or so then introduce to full sunlight (species dependent).
- Keep the bonsai out of extremes such as heat and cold while recovering.